1. Field of the Invention
The present invention relates to a digital video interface and, more specifically, to a digital video interface that uses the clock channel as an auxiliary data channel.
2. Description of the Related Art
Current digital video interfaces such as DVI (Digital Video Interface), HDMI (High-Definition Multimedia Interface), and UDI (Unified Display Interface) typically use 3 or 6 RGB (Red, Green, and Blue video data) channels for the main data stream and 1 clock channel for a frequency reference, in order to transmit digital video data between a video source device (e.g., a digital video disk player) and a video sink device (e.g., a high-definition television). Each channel (R, G, B, and clock) is typically comprised of a differential pair of two matched wires. The clock channel is used to transmit the frequency reference for the digital video data from the video source device to the video sink device, with the clock frequency being set to the video data rate of the digital video data.
In conventional digital video interfaces such as HDMI, the R, G, B data channels transmit video data and control data in an alternating manner with time-division multiplexing. That is, video data is transmitted in certain time slots of the R, G, B data channels while control data is transmitted in other time slots of the R, G, B data channels in an alternating manner. The clock signal is transmitted via the clock channel continuously regardless of whether the R, G, B data channels are used to transmit digital video data or control data.
However, once the RGB links become settled, the frequency information is no longer needed by the video sink side, because the receiver clock and data recovery circuit in the digital video interfaces can keep the link synchronized using the serial RGB data. Thus, conventional digital video interfaces use the clock channel inefficiently, transmitting the clock signal continuously even when the frequency information may not be needed at the video sink. This results in inefficient use of the clock channel.
Thus, there is a need for a technique for using the clock channel of a digital video interface more efficiently.